Personal computers for use at the home or office are becoming increasingly popular. Many applications for these computers require the capability to produce multicolor hard copy graphics. Further, a plotter instrument for providing this capability must be small, preferably desktop positionable, and low cost. These requirements have heretofore been satisfied by such plotter instruments as the HIPLOT.RTM. DMP-29 and DMP-40 plotters offered by Baush & Lomb, Houston Instrument Division. However, these plotters do have certain limitations. For example, multicolor plotting with the DMP-40 requires that the computer program controlling the plotter include a "pause" command to allow pen changing. Although with the DMP-29, there is no need to manually stop the plotter to change pens, there is an increased cost.
Accordingly, there is the need for a low cost, desktop plotter instrument for multicolor plotting under computer control without need of "pause" commands to manually stop operation for pen changing.